\begin{tikzpicture}
	\pgfmathsetmacro{\a}{1.0}
	\pgfmathsetmacro{\b}{1.5}
	\pgfmathsetmacro{\c}{2.0}
	\tkzDefPoints{0/0/A1, \a/0/A2, 1.3/0/B1, 1.3+\b/0/B2, 3.1/0/C1, 3.1+\c/0/C2}
	\tkzDrawSegments[xianduan={below=0pt}](A1,A2  B1,B2  C1,C2)
	\tkzLabelSegment[above](A1,A2){$a$}
	\tkzLabelSegment[above](B1,B2){$b$}
	\tkzLabelSegment[above](C1,C2){$c$}
\end{tikzpicture}

